1. Field of the Invention
The present invention relates to a battery pack apparatus containing a primary or secondary battery, and a method of controlling the battery pack apparatus; in particular, the present invention relates to a battery pack apparatus capable of detecting a battery removed state, and a method of controlling the battery pack apparatus.
2. Description of the Related Art
There has been known a battery protection circuit that prohibits charge and discharge by blowing a thermal fuse using a heat element when abnormality such as overvoltage of a battery is detected. For example, Japanese Unexamined Patent Application Publication No. 2000-357540 discloses such battery protection circuit that blows the thermal fuse using a heat element and stops charge and discharge when overvoltage of a battery is detected.
Further, Japanese Patent No. 2576525 discloses a battery pack apparatus including a secondary battery detachable from an electronic apparatus. Characteristic data on the secondary battery stored in a nonvolatile memory incorporated in the battery pack apparatus are occasionally updated to obtain an accurate characteristic of the secondary battery. The above-described patent discloses a battery pack apparatus including a nonvolatile memory, while a computer (hereinafter described as CPU) based automatic measuring unit is provided to a charging apparatus. In the case where the battery pack apparatus is held by the charging apparatus, the number of charges, a discharge characteristic, and the like are automatically measured to calculate and display the capacity of the battery based on such data. Further, the data on the discharge characteristic and capacity are stored in the nonvolatile memory included in the battery apparatus. Therefore, battery life can be predicted, and the battery can be used economically and efficiently.
FIG. 1 is a diagram showing a system disclosed in Japanese Patent No. 2576525. A battery pack apparatus 1 stores a battery group (hereinafter described as a battery cell) 2 including, for example, a plurality of nickel-cadmium batteries connected in series as shown with a dotted line 2, and a nonvolatile memory 3 formed of, for example, an EEPROM. A connection terminal 4 led from the +(positive) electrode of the battery cell 2, a connection terminal 5 led from the −(negative) electrode thereof, and an input-output terminal 6 led from the nonvolatile memory 3 are provided to predetermined positions on the outside surface of a housing of the battery pack apparatus 1. A charging apparatus 7 includes an automatic measuring unit having a CPU 14, thereby automatically measuring the number of charges, a discharge characteristic, and the like.
An A/D converter 13, heater 21, cooler 22, switch circuit 15, display unit 19, switch group 23 and interface circuit 18 are connected to the CPU 14 that serves as a hub of the control, and an input-output terminal 10 is led from the CPU 14. Further, an external input-output terminal 20 is led from the interface circuit 18. It should be noted that, although not shown in the figure, the CPU 14 includes a ROM incorporating control software, input-output apparatus, and the like.
Further, a holding space 11 to store the battery pack apparatus 1 is formed in the charging apparatus 7. A connection terminal 8 led from a terminal 15a of the switch circuit 15, a terminal 9 led from a terminal 15b thereof, and the input-output terminal 10 led from the CPU 14 are provided to predetermined positions on the outside surface of the housing forming the holding space 11. The heater 21 and cooler 22 are provided on the outside surface of the housing forming the holding space 11, and further, a temperature sensor 12 is provided. The heater 21 and cooler 22 are driven by a control signal from the CPU 14, and turned on so that the charge of the battery cell 2 in the battery pack apparatus 1 is optimized under a temperature condition within a predetermined range.
A charge circuit 16 is connected between a terminal 15c and terminal 15f of the switch circuit 15, and a rated load 17 is connected between a terminal 15e and a terminal 15h. Further, a terminal 15d and terminal 15g of the switch circuit 15 are open. The switch circuit 15 has a control terminal to which a control signal is supplied from the CPU 14, and the predetermined terminal 15a (15b) is selectively connected to the terminals 15c, 15d, 15e (15f, 15g, 15h). Specifically, when charging, the terminal 15a is connected to the terminal 15c, and the terminal 15b is connected to the terminal 15f. Further, when measuring a discharge characteristic, the terminal 15a is connected to the terminal 15e, and the terminal 15b is connected to the terminal 15h. Except for charging and measuring the discharge characteristic, the terminal 15a is connected to the terminal 15d, and the terminal 15b is connected to the terminal 15g. 
Further, the connection terminal 8 and temperature sensor 12 are connected to the A/D converter 13 connected to the CPU 14. Thus, data on the terminal voltage of the battery cell 2, an ambient temperature, and the like are input into the CPU 14 via the A/D converter 13, according to need. The CPU 14 enters various modes corresponding to the operations using the switch group 23, a signal indicating that the battery pack apparatus 1 has been stored in the holding space 11, and the like. Further, the CPU 14 conducts various kinds of processing so as to control respective units, prepares a display signal according to need, and supplies the display signal to the display unit 19 to display predetermined information.
For example, as shown by the dotted-line arrows, the connection terminal 4 of the battery pack apparatus 1 is connected to the connection terminal 8 of the charging apparatus 7, and the connection terminal 5 of the battery pack apparatus 1 is connected to the connection terminal 9 of the charging apparatus 7 in the state of the battery pack apparatus 1 being stored in the holding space 11. In addition, the input-output terminal 6 of the battery pack apparatus 1 is connected to the input-output terminal 10 of the charging apparatus 7, thereby coupling the nonvolatile memory 3 to the CPU 14. If an external input apparatus is connected to the external input-output terminal 20 in such state, the nonvolatile memory 3 is brought into a writing state. Subsequently, data indicating, for example, the name of administrator, start date of use, ID number, and the like are written from the connected external input apparatus, are supplied to the nonvolatile memory 3 and stored in a predetermined region thereof via the interface circuit 18 and CPU 14.
Further, upon storing the battery pack apparatus 1 in the holding space 11, the CPU 14 automatically retrieves data on the number of charges stored in the nonvolatile memory 3, and displays the number of charges on the display unit 19. If a charging mode is selected, the CPU 14 operates the heater 21 and cooler 22 based on the value supplied from the temperature sensor 12, controls the ambient temperature of the battery pack apparatus 1 to be an optimum temperature, and connects the charge circuit 16 to the battery cell 2 to charge in that state. Further, the CPU 14 obtains a value of the terminal voltage of the battery cell 2 and monitors the value. If more voltage drop than a predetermined level is detected, the CPU 14 terminates charging, updates a flag indicating the number of charges, and stores data on the number of charges and the like in the nonvolatile memory 3. Further, the CPU 14 is selectively in the discharge characteristic measurement mode once every predetermined number of times, connects the rated load 17 to the battery cell 2, obtains the terminal voltage, and collects data on the terminal voltage with a predetermined period until the terminal voltage decreases to a predetermined level. With the terminal voltage having the predetermined level and the discharge characteristic measurement having been over, the CPU 14 calculates and displays the battery capacity based on the data on the terminal voltage, and stores data on the discharge characteristic measurement and the battery capacity in the nonvolatile memory 3.
Various kinds of data intensively stored in the nonvolatile memory 3 through the above-mentioned processing are retrieved by the operation using the switch group 23 and processing steps at the CPU 14 according to need, and are input into the CPU 14. Display signals corresponding to the various data are prepared in the CPU 14, and supplied to the display unit 19 to be displayed as information by means of characters and the like. Further, in the case where an external output apparatus such as a printer is connected to the external input-output terminal 20, data stored in the nonvolatile memory 3 and data generated by the processing of the CPU 14 are retrieved according to need, and output in the form of hard copy. Hence, a user can readily determine the battery life comprehensively and can manage battery history by referring to such information as the battery capacity, number of charges, start date of use and the like displayed according to the processing steps and according to need.